Study of correlation between radon (222Rn) gas in soil and indoor radon with dose assessment in the bauxite bearing area of Fongo-Tongo, Western Cameroon

Abstract

ABSTRACT The aim of the current work is to study the correlation between 222Rn gas in soil and indoor 222Rn concentrations. Markus 10 and RADTRAK detectors were used to measure 222Rn concentrations at 1 m depth in soil 30 points and 50 dwellings respectively. These concentrations varied from 35 kBq m−3 to 255 kBq m−3 with a geometric mean of 67 (18) kBq m−3, and from 85 Bq m−3 to 410 Bq m−3, with a geometric mean of 152 (26) Bq m−3 respectively in the soil gas and dwellings. In additional, 99% of the measurement points had concentrations higher than the limit value of 40 kBq m−3 according to the Swedish criterion for risk levels; 94% of the houses had radon concentrations higher than 100 Bq m−3, the reference value of the World Health Organization (WHO). When there was not a good air flow between the outside and the inside of the dwelling, the correlation coefficients were R2 = 0.82 and R2 = 0.73 respectively for the earthen and concrete dwellings. Under the best natural ventilation conditions, these correlation coefficients decrease significantly. Their values were R2 = 0.54 and R2 = 0.34 respectively for the earthen and concrete dwellings. Furthermore, a RadonEye +2 detector revealed a daily 222Rn accumulation reaching values of 800 Bq m−3 in some dwellings when all doors and windows were closed. Architecturally, dwellings built with sealed materials such as cement and concrete, whose do not facilitate 222Rn diffusion and transport, have lower 222Rn concentrations and effective dose than others These results show that 222Rn gas in soil and in confined air in dwellings are strongly correlated.